Element X should not blindly use `bump_stamp` for sorting.

[Kladki]

Currently, Element X Android seems to blindly sort rooms as per bump_stamp. However, bump_stamp is based on the ordering the server has of the most recent event of the room, no matter the type of event. This can lead to seemingly inconsistent ordering, due Element X Android not actually showing certain events (e.g. avatar/display name changes) in the timeline, causing the rooms to be bubbled up to the top for seemingly no reason.

Either Element X Android should be aware of this and perform some sort of client-side ordering, or the sliding sync MSC should be updated to allow the client to communicate in some way what events types should be considered for the bump_stamp ordering (and should be sent down more generally).